Elemental characterization of mineral supplements by neutron activation analysis

Instrumental neutron activation analysis (INAA) was applied to assess element concentrations in eleven samples of mineral supplements/multivitamins acquired in drugstores and pharmacies in São Paulo city, SP, Brazil. Concentrations of Ca, Co, Cr, Cu, Fe, K, Na, Se and Zn were determined. A comparison was made between the results obtained with the labels of the mineral supplents. Certified reference materials, NIST SRM1400 Bone Ash and NIST SRM 1633b Coal Fly Ash were analyzed for quality control of the analytical results.     

Use of neutron activation analysis for the characterization of single-wall carbon nanotube materials

Instrumental neutron activation analysis (INAA) and prompt gamma neutron activation analysis (PGAA) were used to characterize a variety of single-wall carbon nanotube (SWCNT) materials from different principal production processes, as well as a material containing SWCNTs together with other carbon species, catalyst residues, and trace element contaminants to be issued by the National Institute of Standards and Technology for characterization and distribution as Standard Reference Material SRM 2483 Carbon Nanotube Soot. INAA proved to be well suited for the direct determination of catalyst and contaminant trace elements requiring only minimal sample preparation. PGAA complemented the INAA data in particular with determinations of the light elements. Carbon and hydrogen results provided information on the materials purity and storage properties. Strategies for the quality assurance of the measurements in these new materials were developed. INAA and PGAA data were provided for the value assignment of mass fractions of catalyst and trace elements in the candidate SRM and a systematic overview was obtained of the catalyst and trace element contaminants associated with each of the major production routes.     

Use of INAA,PGAA, and RNAA to determine 30 elements for certification of an SRM: Tomato Leaves, 157a

Analyses for certification have been made for the determination of 30 elements in the National Institute of Standards and Technology (NIST) Tomato Leaves renewal reference material, SRM 1573a. Three of the analytical techniques used were instrumental neutron activation analysis (INAA), radiochemical neutron activation analysis (RNAA), and prompt gamma activation analysis (PGAA). These techniques provided data on 19 elements by INAA, 10 elements by PGAA, and 7 elements by RNAA, with some overlap between techniques. For example, INAA was able to obtain overall analytical uncerainties (at the 95% confidence level) averaging ±2.2% for major and minor constituents (Ca, Mg, K), ±3.3% for constituents from 1 to 1000 g/g (Na, Fe, Al, Mn, Ba, Zn, Rb, La, Cr), and ±6.4% for elements between 10 and 1000 ng/g (Co, V, Se, Th, Sc, Sb), using sample dry weights of approximately 150 mg. These analyses represent the most extensive use to date of nuclear analytical techniques in the certification of a trace element SRM at NIST.     

Revalidation and long-term stability of National Institute of Standards and Technology Standard Reference Materials 1566, 1567, 1568, and 1570

Multiple units of Standard Reference Materials (SRMs) 1566 Oyster Tissue, 1567 Wheat Flour, 1568 Rice Flour, and 1570 Trace Elements in Spinach, produced by the National Institute of Standards and Technology (NIST, then the National Bureau of Standards), were analyzed 17-20 years after the original certification dates and 12-15 years after the certificates became invalid. Instrumental neutron activation analysis and thermal neutron prompt gamma-ray activation analysis were used to measure mass fractions for 27 elements in these SRMs to revalidate them for use in quality assurance (QA) programs required for food analysis programs within the U.S. Food and Drug Administration. With the exception of Se in SRM 1567, all element mass fractions were in agreement with certified values and literature data. Some evidence of B loss from SRM 1568 was observed. These materials were judged to be suitable for continued use in QA programs. Findings showed that these matrixes exhibited stability of moisture, mass fraction, and weight basis for far longer (> or =15 years) than was indicated by the 5-year validity statement on the NIST Certificates of Analysis.     

Neutron Capture Prompt Gamma-Ray Activation Analysis of Meat Homogenates

Thermal neutron capture prompt gamma-ray activation analysis (PGAA) was used to determine mass fractions of H, B, C, N, Na, Cl, K, and S in 2 meat homogenates. Twelve units of candidate Standard Reference Material (SRM) 1546 Meat Homogenate produced by the National Institute of Standards and Technology (NIST) were analyzed to provide NIST with certification data. This SRM is a realistic processed food matrix, ideal for food analysis programs such as the Food and Drug Administration's Total Diet Study. Another meat homogenate, Certified Reference Material LGC 7002 Pork/Chicken (along with NIST SRMs 1549 Non-Fat Milk Powder and 1571 Orchard Leaves) was analyzed for quality control. Candidate SRM 1546 unit-to-unit heterogeneity was <2% for H, Na, Cl, and K, and 3.5% for N and within-unit heterogeneity was <2% for H, N, Cl, and K, and 2.9% for Na, similar to LGC 7002 homogeneity results. Control material mass fractions agreed well with certificate and consensus values. Protein mass fractions, calculated from N results, were 15.2% and 11.9% for candidate SRM 1546 and LGC 7002, respectively. Protein content calculated for SRM 1549 (36.0%) agreed well with known values for dried non-fat milk powder.     

Determination of rare earth elements in chloroplasts of Brassia napus by INAA and biochemical separation techniques

Intact chloroplasts were isolated from mesophyll protoplasts of Brassia napus. Concentrations of 8 rare earth elements (REEs) in the chloroplasts were determined by instrumental neutron activation analysis (INAA). The results showed that there were trace amounts of REEs in the chloroplasts, which corresponded to 1 atom of REEs per 2000 chlorophyll molecules. About 30% of the total REEs in the leaves are localized in the chloroplasts and the light REEs were enriched with respect to the heavy elements of the series.     

The simultaneous determination of 235U and 239Pu using delayed neutron activation analysis

Delayed neutron activation analysis (DNAA) remains one of the most sensitive methods of nondestructively determining fissile materials in a variety of sample matrices, provided that the samples contain only a single fissile component. This has historically been the limiting factor in many applications of DNAA, and often chemically destructive methods of analysis have needed to be utilized for many real-world samples. This work seeks to develop a method that will allow for DNAA to be utilized on samples containing multiple fissile components. Initial efforts, presented here, show that using a multivariate linear regression model to describe the delayed neutron emission profile of an irradiated sample allows for the concurrent determination of fissile nuclides in samples containing both ²³⁵U and ²³⁹Pu, without chemical separations and using only a single counting step.     

U determination in environmental samples by delayed neutron activation analysis in Korea

A delayed neutron counting system has been implemented at the HANARO research reactor in 2007. Thermal neutron flux measured at the NAA #2 irradiation hole coupled to the delayed counting system, was higher than 3 × 10¹³ n cm⁻² s⁻¹. The delayed neutron counting system is composed of 18 ³He detectors which are divided into three groups with six detectors and the collected signals of each group are processed to a digital signal. The count numbers were measured with the uranium mass by using NIST SRMs under fixed analytical condition and their correlation could be determined. Finally, delayed neutron activation analysis has been carried out for the determination of uranium mass fraction in the collected environmental samples.     

Delayed neutron activation analysis for safeguards

Delayed neutron activation analysis (DNAA) presents a fast, accurate, and reliable method for quantification of fissile material. The method has relatively few sources of error and may be accomplished nondestructively. The need for a fast, accurate screening of materials stems from the necessity to protect cleanroom facilities from widely varying fissile quantities in samples and from desired gains in efficiency of mass spectrometric analysis by assisting in spike level selection and by removing from the sample set those materials that are not of interest. During the last several years, many different materials have been screened or analyzed in support of international safeguards, internal process control for actinide separations, and in uranium contamination assessments. Swipes from a variety of sources have been analyzed, either before or after dissolution, and comparison of the DNAA results to mass spectrometry results is generally favorable. A facility characterization of the High Flux Isotope Reactor was performed using filter paper swipes to demonstrate the utility of the DNAA technique.     

REE bound DNA in natural plant

The binding of rare earth elements (REEs) with nucleic acids in the leaves of fern Dicranopteris dichotoma (DD) has been studied by molecular activation analysis (MAA). The REEs bound DNA (REE-DNA) was obtained from the leaves of DD. The CTAB-based procedure was modified for extraction of total DNA. The purity of DNA was examined by UV spectroscopy. The DNA obtained was separated and determined by agarose gel electrophoresis further. Meanwhile, the contents of eight rare earth elements (La, Ce, Nd, Sm, Eu,Tb, Yb and Lu) in REE-DNA were detected by instrumental neutron activation analysis (INAA). The results showed that REE-DNA with higher purity could be extracted from plant using this method. It was also found that REEs were bound firmly with DNA in the leaves of DD. The molecular weight (MW) of REE-DNA band was about 22 kb in agarose gel electrophoresis.     

Determination of valuable elements in natural phosphates

Natural phosphates are used on large scale in the fertilizer industry. The usual process of the chemical attack is sulfuric (predominant) and nitric acids. The liquid phosphoric acid phase resulted contains dissolved valuable elements like: uranium and rare earths elements (REEs). Uranium and REEs are recovered in some technologies as valuable products. It is therefore important to know, uranium and REEs content in natural phosphates in view to decide on their recovery. In this paper determinations were carried out to find the uranium and REEs contents. The concentrations involved are low, therefore, it is difficult to find a classical reliable method without incurring important losses, i. e., errors. In this work uranium and REEs were determined by physical methods like: neutron activation analysis (NAA), emission spectroscopy, mass spark spectrometry and X-ray fluorescence. The results obtained were acceptable and intercomparison between various methods was carried out. It was found that most reliable results were given by mass spark spectrometry and activation analysis. The data resulted are in good agreement with uranium and REEs in the green cake (uranium tetrafluoride) and in the REEs concentrate obtained by solvent, extraction from phosphoric acid.     

Determination of boron in materials by cold neutron prompt gamma-ray activation analysis

An instrument for cold neutron prompt gamma-ray activation analysis (PGAA), located at the NIST Center for Neutron Research (NCNR), has proven useful for the measurement of boron in a variety of materials. Neutrons, moderated by passage through liquid hydrogen at 20 K, pass through a (58)Ni coated guide to the PGAA station in the cold neutron guide hall of the NCNR. The thermal equivalent neutron fluence rate at the sample position is 9 x 10(8) cm(-2) s(-1). Prompt gamma rays are measured by a cadmium- and lead-shielded high-purity germanium detector. The instrument has been used to measure boron mass fractions in minerals, in NIST SRM 2175 (Refractory Alloy MP-35-N) for certification of boron, and most recently in semiconductor-grade silicon. The limit of detection for boron in many materials is <10 ng g(-1).     

Assessment of stability of trace elements in two natural matrix environmental standard reference materials: NIST-SRM 1547 Peach leaves and NIST-SRM 1566a Oyster Tissue

The NIST program for environmental Standard Reference Materials (SRM) includes materials covering a range of matrices, mass fraction values and analytes. For many SRMs, mass fraction data are accumulated, incidentally, over time, as these are used routinely for quality assurance purposes. Although these are not formal stability studies, data generated may be useful in assessing stability. To evaluate the potential for assessing material stability from incidental use of SRMs, results of neutron activation analysis performed from 1992 through 2008 were compiled for SRM 1547 Peach Leaves and SRM 1566a Oyster Tissue. Results indicate that incidental use of SRMs yields useful information on SRM stability.     

Characterisation of biological RMs for potential use in human brain analysis

Summary In order to investigate the precision and accuracy obtainable with instrumental neutron activation analysis (INAA) and inductively coupled plasma atomic emission spectrometry (ICP-AES), five different biological reference materials were analyzed. Four of them originated from the US National Institute of Standards and Technology (NIST) (Bovine Liver (SRM 1577; 1577/a; 185/A), Orchard Leaves (SRM 1571)) and one of them came from the International Atomic Energy Agency (IAEA) (Animal muscle (H-4)). The decomposition efficiency of microwave acid digestion was examined in comparison to digestions carried out in a Parrbomb. Five to ten subsamples of each material were subjected to the two digestion procedures and the solutions were analyzed by ICP-AES. The dried samples were analyzed by INAA. Up to 16 elements (Al, B, Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, S, Zn) were determined in various materials.     

Radioanalytical methods for the non-destructive analysis of lunar samples

The elemental compositions of Apollo 11 and Apollo 12 lunar soil samples 10084,141 and 12070,83 and Apollo 12 rock fragment 12063,73 were determined by non-destructive radioanalytical methods. Main mineral fractions and glasses separated from these samples were analyzed as well. Instrumental neutron activation analysis (INAA) was used to determine Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Cs, Ba La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb, Lu, Hf, Ta, W, Ir, Au, Th and U. A method of delayed neutron counting was used for the determination of uranium, and non-dispersive radioisotopic X-ray fluorescence analysis was applied to the determination of Ti, Fe, Sr, Y and Zr.     

Determination of arsenic in food and dietary supplement standard reference materials by neutron activation analysis

Arsenic was measured in food and dietary supplement standard reference materials by neutron activation analysis for the purpose of assigning certified or reference As mass fractions and to assess material homogeneity. Instrumental neutron activation analysis was used to value assign As in candidate SRM 3532 Calcium Dietary Supplement and candidate SRM 3262 Hypericum perforatum (St. John’s Wort) Aerial Parts down to about 100 μg/kg. Values were also determined for two additional candidate St. John’s Wort SRMs with As mass fractions <100 μg/kg. The presence of significant amounts of ²⁴Na and ⁸²Br limited the reproducibility of the method below 100 μg/kg. For measurement of lower As mass fractions, a radiochemical neutron activation analysis method with extraction of As³⁺ into diethyl-dithiocarbamate in chloroform and detection limits down to 0.1 μg/kg. As was used to value-assign As mass fractions for SRM 3280 Multivitamin/Multielement Tablets and for candidate SRM 3233 Fortified Breakfast Cereal, and at <10 μg/kg in candidate SRM 1845a Whole Egg Powder.     

Elemental composition changes in citrus affected by the CVC disease

The citrus variegated chlorosis (CVC) disease results in serious economical losses for the Brazilian citriculture. The influence of CVC disease on the elemental composition of citrus plants was investigated. Leaves of sweet orange varieties Hamlin, Pera Rio and Valencia were collected from healthy and CVC-affected trees for chemical characterization by instrumental neutron activation analysis (INAA). Significant differences between healthy and CVC-affected leaves were identified for Ca, Ce, Co, Eu, Fe, K, La, Na, Nd, Rb, Sc and Sm. Rare earth elements presented consistently higher mass fractions in the healthy leaves.     

Neutron activation analysis with pre- and post-irradiation chemical separation for the value assignments of Al, V, and Ni in the new bovine liver SRM 1577C

Instrumental neutron activation analysis as carried out at the National Institute of Standards and Technology (NIST) is inadequate for determining Al, Ni, and V at the levels found in the newly prepared Standard Reference Material^® (SRM) 1577c Bovine Liver. To overcome shortcomings in the value assignment, the authors initiated a cooperative approach using NAA with previously established chemical separation procedures and with significantly different neutron energy spectra to determine Al and V with pre-irradiation separation of the elements at NIST, and V and Ni with post-irradiation separation at the Nuclear Physics Institute ?e?. The determinations were confirmed with the analyses of several SRMs. The work supported the certification of mass fraction values for V and Ni in SRM 1577c.     

Instrumental Neutron Activation Analysis for Certification of Ion-Implanted Arsenic in Silicon

Standard reference material (SRM) 2134 Arsenic Implant in Silicon was produced at the National Institute of Standards and Technology (NIST) as a calibrant for secondary ion mass spectrometry. Instrumental neutron activation analysis was used as a primary method for certification of the arsenic implanted dose. A complete evaluation of all sources of uncertainty yielded an expanded relative uncertainty for the mean value of this SRM to be 0.38% at approximately the 95% level of confidence. No evidence indicating significant heterogeneity among samples was observed.